Magnetic Sensor Array With Single TMR Film Plus Laser Annealing And Characterization

ABSTRACT

The present disclosure generally relates to a Wheatstone bridge array that has four resistors. Each resistor includes a plurality of TMR films. Each resistor has identical TMR films. The TMR films of two resistors have reference layers that have an antiparallel magnetic orientation relative to the TMR films of the other two resistors. To ensure the antiparallel magnetic orientation, the TMR films are all formed simultaneously and annealed in a magnetic field simultaneously. Thereafter, the TMR films of two resistors are annealed a second time in a magnetic field while the TMR films of the other two resistors are not annealed a second time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/879,601, filed May 20, 2020, which application claims benefit of U.S.Provisional Patent Application Ser. No. 62/954,199, filed Dec. 27, 2019,each of which is herein incorporated by reference.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

Embodiments of the present disclosure generally relate to a Wheatstonebridge array and a method of manufacture thereof.

Description of the Related Art

A Wheatstone bridge is an electrical circuit used to measure an unknownelectrical resistance by balancing two legs of a bridge circuit, one legof which includes an unknown component. The Wheatstone circuit providesextremely accurate measurements in comparison to a simple voltagedivider.

The Wheatstone bridge includes multiple resistors that, especiallyrecently, include magnetic material such as a magnetic sensors. Magneticsensors can include Hall effect magnetic sensors, anisotropymagnetoresistive sensors (AMR), giant magnetoresistive (GMR) sensors,and tunnel magnetoresistive (TMR) sensors. The TMR sensor has a veryhigh sensitivity compared to other magnetic sensors.

The Wheatstone bridge array has a linear output signal and resists theenvironment temperature. Any temperature change in the Wheatstone bridgearray is cancelled. The Wheatstone bridge array has four resistors. Twoof the resistors have identical resistance while the remaining tworesistors have identical resistances relative to each other, butdifferent from the original two resistors.

Fabricating different resistors to achieve different resistances can becostly and time consuming. Therefore, there is a need in the art for aWheatstone bridge array that can be fabricated in a cost effective andtime sensitive manner.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to a Wheatstone bridge arraythat has four resistors. Each resistor includes a plurality of TMRfilms. Each resistor has identical TMR films. The TMR films of tworesistors have reference layers that have an antiparallel magneticorientation relative to the TMR films of the other two resistors. Toensure the antiparallel magnetic orientation, the TMR films are allformed simultaneously and annealed in a magnetic field simultaneously.Thereafter, the TMR films of two resistors are annealed a second time ina magnetic field while the TMR films of the other two resistors are notannealed a second time.

In one embodiment, a TMR sensor device comprises: a first resistorcomprising at least one first tunnel magnetoresistive (TMR) film havinga first reference layer; and a second resistor comprising at least onesecond TMR film having a second reference layer, wherein the first TMRfilm and the second TMR film are substantially identical, and whereinthe first reference layer and the second reference layer have anantiparallel magnetic orientation.

In another embodiment, a TMR sensor device comprises four resistors,wherein each resistor includes at least one tunnel magnetoresistive(TMR) film that includes a reference layer, wherein the TMR films areidentical in each resistor, and wherein the reference layer of at leasttwo TMR films have an antiparallel magnetic orientation.

In another embodiment, a method of manufacturing a TMR sensor devicecomprises: forming a first tunnel magnetoresistive (TMR) film on asubstrate; forming a second TMR film on the substrate; annealing thefirst TMR film and the second TMR film in a magnetic field; andannealing the second TMR film a second time in a magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 is a schematic illustration of a Wheatstone bridge array design.

FIGS. 2A-2G are schematic illustrations of TMR structures at variousstages of manufacture according to one embodiment.

FIGS. 3A and 3B are schematic illustrations of TMR structures prior toand after the first annealing according to one embodiment.

FIG. 3C is schematic illustration of TMR structures after the secondannealing according to one embodiment.

FIG. 4 is a graph illustrating the R-H curve of TMR films 200, 250following the second annealing.

FIG. 5 is a graph illustrating the resistance area and TMR for a TMRfilm that has been annealed according to one embodiment.

FIG. 6 is a schematic illustration of a Wheatstone bridge array withmultiple TMR structures for each resistor.

FIG. 7 is a flowchart illustrating a method of manufacturing aWheatstone bridge array.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

In the following, reference is made to embodiments of the disclosure.However, it should be understood that the disclosure is not limited tospecific described embodiments. Instead, any combination of thefollowing features and elements, whether related to differentembodiments or not, is contemplated to implement and practice thedisclosure. Furthermore, although embodiments of the disclosure mayachieve advantages over other possible solutions and/or over the priorart, whether or not a particular advantage is achieved by a givenembodiment is not limiting of the disclosure. Thus, the followingaspects, features, embodiments and advantages are merely illustrativeand are not considered elements or limitations of the appended claimsexcept where explicitly recited in a claim(s). Likewise, reference to“the disclosure” shall not be construed as a generalization of anyinventive subject matter disclosed herein and shall not be considered tobe an element or limitation of the appended claims except whereexplicitly recited in a claim(s).

The present disclosure generally relates to a Wheatstone bridge arraythat has four resistors. Each resistor includes a plurality of TMRfilms. Each resistor has identical TMR films. The TMR films of tworesistors have reference layers that have an antiparallel magneticorientation relative to the TMR films of the other two resistors. Toensure the antiparallel magnetic orientation, the TMR films are allformed simultaneously and annealed in a magnetic field simultaneously.Thereafter, the TMR films of two resistors are annealed a second time ina magnetic field while the TMR films of the other two resistors are notannealed a second time.

FIG. 1 is a schematic illustration of a Wheatstone bridge array 100design. The array 100 includes a bias source 102, a first resistor 104,a second resistor 106, a third resistor 108, a fourth resistor 110, afirst sensor 112, a second sensor 114, and a ground connection 116. Biasvoltage is applied across the array from the bias source 102 to theground connection 116. The first sensor 112 and the second sensor 114sense the output of the applied voltage. Any temperature change from theresistors 104, 106, 108, 110 can be cancelled.

As discussed herein, the resistors 104, 106, 108, 110 each include a TMRsensor. In one embodiment, the TMR sensors are each distinct anddifferent such that the resistors 104, 106, 108, 110 have differentresistance. In another embodiment, the TMR sensors are identical, butthe resistors 104, 106, 108, 110 are different. In still anotherembodiment, resistors 104, 110 are identical to each other (as are theTMR sensors that comprise the resistors 104, 110), and resistors 106,108 are identical to each other (as are the TMR sensors that comprisethe resistors 106, 108) yet different from resistors 104, 110. For a TMRsensor in array 100, the RA for the array 100 is around 100 Ohmsmicrons².

Typical magnetic field sensors use MR (magnetoresistance) devices in aWheatstone bridge circuit. The sensor requires the MR devices to changedifferently in the bridge. As discussed herein, a new method to make amagnetic field sensor is to fabricate two different TMR films in thesame layer. The reliability and performance of the TMR films determinesthe magnetoresistance response. In this way, combined with different TMRfilms features, a perfect Wheatstone bridge design for magnetic fieldsensor can be fabricated.

In regards to FIG. 1, if the free layer of the TMR sensors thatcomprises the resistors 104, 106, 108, 110 has a long axis of +45° or−45° to the pinned layer magnetization direction, then the free layereasy axis is restricted to be along the long axis due to the shapeanisotropy, and the magnetization direction can be set as shown in FIG.1 by an ampere field from the set line current, especially if on top ofthe free layer there is a set line orthogonal to the free layer longaxis.

When applying a magnetic field along the Y-axis, resistors 110 and 104are increasing while resistors 106, 108 are decreasing with the field.This different response enables the Wheatstone bridge, and the sensorsensitivity is proportional to the output voltage which is proportionalto the difference between resistor 110 (or resistor 104) and resistor106 (or resistor 108). However, in use only half of themagnetoresistance change is used due to the 45° free layer or pinnedlayer initial state. If the free layer to pinned layer initial state canbe 90° and still have two different magnetoresistance change, the sensorsensitivity can be increased by a factor of two.

If the free layer and pinned layer are orthogonal, then the pinned layermagnetization direction is set by magnetic annealing direction. Usuallyresistors 104, 106, 108, 110 are made by the same TMR film andexperience the same processes, and therefore all have the same pinnedlayer direction. Each device can operate in full MR ratio, but all thedevices respond to the external field in the same way and consequentlythere is no output voltage at all. A simple way to resolve this issue isto shield resistor 106 and resistor 108 by covering with a thick NiFefilm so that resistor 106 and resistor 108 will not respond to magneticfields. Alternatively, resistors 106 and 108 can be replaced withconstant resistors. However, this kind of half bridge-sensing schemewill also reduce the output voltage and therefore limits thesensitivity.

FIGS. 2A-2G are schematic illustrations of TMR structures 200, 250 atvarious stages of manufacture according to one embodiment. As shown inFIG. 2A, each TMR structure 200, 250 includes a seed layer 202. The seedlayers 202 are formed simultaneously for each TMR structure 200, 250. Itis to be understood that the terms TMR structure, TMR sensor, and TMRfilm may be used interchangeably throughout the description. In oneembodiment, the seed layer 202 comprises a conductive material such asruthenium and has a thickness of between about 10 Angstroms to about 100Angstroms and is deposited by well-known deposition methods such aselectroplating, electroless plating, or sputtering. Additionally, it isto be understood that while ruthenium has been exemplified as the seedlayer 202 material, other materials are contemplated and the embodimentsdiscussed herein are not limited to ruthenium for the seed layer 202.

An antiferromagnetic (AFM) layer 204 is disposed on the seed layer 202as shown in FIG. 2B. Suitable materials for the AFM layer 204 includeIrMn or PtMn at a thickness of between about 40 Angstroms to about 500Angstroms such as between about 40 Angstroms and about 100 Angstroms.The AFM layer 204 may be formed by well-known deposition methods such assputtering. Additionally, it is to be understood that while IrMn andPtMn have been exemplified as the AFM layer 204 materials, othermaterials are contemplated and the embodiments discussed herein are notlimited to IrMn or PtMn for the AFM layer 204.

A pinned layer 206 is disposed on the AFM layer 204 as shown in FIG. 2C.Suitable materials for the pinned layer 206 include CoFe, or aCo/CoFe/Co multi-layer stack with a thickness of between about 20Angstroms and about 30 Angstroms. The pinned layer 206 may be formed bywell-known deposition methods such as sputtering. Additionally, it is tobe understood that while CoFe or Co/CoFe/Co have been exemplified as thepinned layer 206 material, other materials are contemplated and theembodiments discussed herein are not limited to CoFe or Co/CoFe/Co forthe pinned layer 206. The pinned layer is pinned by the AFM layer 204and thus the magnetic moment of the pinned layer 206 will not changewhen an external field is applied.

A spacer layer 208 is disposed on the pinned layer 206 as shown in FIG.2D. Suitable materials for the spacer layer 208 includes Ru at athickness of between about 4 Angstroms to about 10 Angstroms. The spacerlayer 208 may be formed by well-known deposition methods such assputtering. Additionally, it is to be understood that while rutheniumhas been exemplified as the spacer layer 208 material, other materialsare contemplated and the embodiments discussed herein are not limited toruthenium for the spacer layer 208.

A reference layer 210 is disposed on the spacer layer 208 as shown inFIG. 2E. Suitable materials for the reference layer 210 includeCoFe/Ta/CoFeB/CoFe as a multilayer stack. The first CoFe layer may havea thickness of between about 8 Angstroms to about 10 Angstroms. The Talayer may have a thickness of between about 0.5 Angstroms to about 2Angstroms. The CoFeB layer may have a thickness of between about 10Angstroms to about 15 Angstroms. The second CoFe layer may have athickness of between about 3 Angstroms to about 10 Angstroms. Thereference layer 210 may be formed by well-known deposition methods suchas sputtering. Additionally, it is to be understood that whileCoFe/Ta/CoFeB/CoFe has been exemplified as the reference layer 210material, other materials are contemplated and the embodiments discussedherein are not limited to CoFe/Ta/CoFeB/CoFe for the reference layer210. The reference layer 210 is antiferromagnetically coupled with thepinned layer 206 through the spacer layer 208 so that the magneticmoment of the reference layer 210 is also fixed.

A barrier layer 212 is disposed on the reference layer 210 as shown inFIG. 2F. Suitable materials for the barrier layer 212 include MgO at athickness of between about 10 Angstroms to about 20 Angstroms. It is tobe understood that while MgO is exemplified as the barrier layer 212,other insulating materials as contemplated.

A free layer 214 is disposed on the barrier layer 212 as shown in FIG.2G. Suitable materials for the free layer 214 include aCoFe/CoFeB/Ta/NiFe multilayer stack. The CoFe layer may have a thicknessof between about 3 Angstroms to about 10 Angstroms. The CoFeB layer mayhave a thickness of between about 10 Angstroms to about 20 Angstroms.The Ta layer may have a thickness of between about 0.5 Angstroms toabout 2 Angstroms. The NiFe layer may have a thickness of between about3 Angstroms to about 300 Angstroms, such as between about 3 Angstromsand about 10 Angstroms or between about 10 Angstroms and about 300Angstroms. The free layer 214 may be formed by well-known depositionmethods such as sputtering. Additionally, it is to be understood thatwhile CoFe/CoFeB/Ta/NiFe has been exemplified as the free layer 214material, other materials are contemplated and the embodiments discussedherein are not limited to CoFe/CoFeB/Ta/NiFe for the free layer 214. Inoperation, the free layer 214 can be slightly biased to obtain a linearsignal that can rotate when an external field is applied. Capping layersmay additionally be formed over the free layer 214.

After film deposition, the TMR films 200, 250 are annealed in vacuumwith a magnetic field applied. In one embodiment, the TMR films 200, 250are annealed in a magnetic oven at a temperature of between about 250degrees Celsius to about 300 degrees Celsius under a magnetic field ofbetween about 10,000 Oe to about 50,000 Oe. FIG. 3A illustrates themagnetic moments of the pinned layer 206, the reference layer 210, andthe free layer 214 prior to annealing. The pinned layer 206 is pinned bythe AFM layer 204 as shown by arrow 302, and the magnetic moment willnot change when an external field is applied. The reference layer 210 isantiferromagnetically coupled with the pinned layer 206 through the thinspacer layer 208 as shown by arrow 304. The magnetic moment of thereference layer 210 is also fixed. The free layer 214 can be slightlybiased to get the linear signal. The magnetic moment of the free layer214 can rotate when an external field is applied as shown by arrow 306.

After annealing, the magnetic moment of the reference layer 210 willhave flipped as shown as arrow 308 in FIG. 3B. In order to obtain twodifferent TMR films 200, 250, a second, selective annealing processoccurs in order to make the references layers 206 antiparallel to eachother. For example, TMR film 250 may selectively annealed while TMR film200 is not annealed. In such a scenario, TMR film 200 may be masked toprevent selective annealing. In one embodiment, rather than masking TMRfilm 200, TMR film 250 is annealed by a focused annealing treatment,such as laser annealing. It is to be understood that TMR film 200 may beselectively annealed while TMR film 250 is not annealed.

To perform the second annealing, initially a film is chosen, such as TMRfilm 250. The TMR film 250 is selectively annealed with a laser togetherwith an external magnetic field. In one embodiment, the laser will be alaser beam and have a size of less than 1 mm. If TMR film 250 isannealed, then TMR film 200 is not annealed in the second annealing.Thus, TMR film 250 will have the magnetic moment of the reference layer210 flipped as shown by arrow 310 while the magnetic moment of thereference layer 210 of TMR film 200 will not flip as shown in FIG. 3C.In one embodiment, the external field applied during the secondannealing is between about 3000 Oe and about 6000 Oe, and the TMR film200 is not masked. The laser may operate at any well-known wavelengthand is not limited to a particular wavelength of operation.

After the second annealing, a current-in-plane tunneling (CIPT) methodis used to characterize the TMR films 200, 250 to make sure the laserannealing resulted in the desired properties. FIG. 4 is a graphillustrating the R-H curve of TMR films 200, 250 following the secondannealing. Because the reference layers 210 have magnetic moments inthat are antiparallel (in other words, opposite magnetic direction), theTMR films 200, 250 will sense the external field differently, one with apositive slope and another with a negative slope. FIG. 5 shows theresistance area (RA) and TMR for both TMR films 200, 250. Using CIPT,the second annealing's impact is confirmed that TMR film 250 has flippedthe magnetic moment of the reference layer 210 without changing the RAand TMR.

FIG. 6 is a schematic illustration of a Wheatstone bridge array 600 withmultiple TMR structures for each resistor R1, R2, R3, R4. R1 maycorrespond to resistor 104; R2 may correspond to resistor 106; R3 maycorrespond to resistor 110; and R4 may correspond to resistor 108. Whenthe working field bias is set to 0, then R1=R2=R3=R4. Additionally, theresistors R1 and R3 are distinct from resistors R2 and R4 based upon theTMR structures to provide two different magnetoresistances responses.

In the array 600, each resistor R1, R2, R3, R4 includes a plurality ofTMR structures 200, 250. More specifically, in one embodiment, resistorsR1 and R3 will include a plurality of TMR structures 200 and resistorsR2 and R4 will include a plurality of TMR structures 250. In anotherembodiment, resistors R1 and R3 will include a plurality of TMRstructures 250 and resistors R2 and R4 will include a plurality of TMRstructures 200. For simplicity, FIG. 6 illustrates resistors R1 and R3having TMR structures 200 while resistors R2 and R4 have TMR structures250. The TMR structures 200, 250 in resistors R1 and R3 are identical inboth number and design. Similarly, the TMR structures 200, 250 inresistors R2 and R4 are identical in both number and design.

FIG. 7 is a flowchart illustrating a method 700 of manufacturing aWheatstone bridge array. The method operates by initially formingmultiple TMR films simultaneously in step 702. The TMR films formedsimultaneously are identical. Then, the TMR films are annealed in afirst annealing process to set the magnetic moment of the referencelayer for each TMR film in step 704. Thereafter, less than all of theTMR films are annealed a second time to flip the magnetic moment of thesecondly annealed TMR films in step 706. During the second annealing,the TMR films that are not annealed will not flip the magnetic moment ofthe reference layer. Thus, the resulting Wheatstone bridge array willhave some TMR films with a reference layer that has a magnetic moment ina first direction while the remaining TMR films will have a referencelayer that has a magnetic moment in a second direction that is opposite,and hence antiparallel, to the first direction. Forming the TMR filmsidentically and subjecting the TMR films to the same first annealingprocess results in an efficiently produced Wheatstone bridge array.Furthermore, not only is there an efficiency realization in terms oftime, but because the TMR films can be fabricated simultaneously, thereis a cost saving as well.

In one embodiment, a TMR sensor device comprises: a first resistorcomprising at least one first tunnel magnetoresistive (TMR) film havinga first reference layer; and a second resistor comprising at least onesecond TMR film having a second reference layer, wherein the first TMRfilm and the second TMR film are substantially identical, and whereinthe first reference layer and the second reference layer have anantiparallel magnetic orientation. The Wheatstone bridge array furthercomprises a third resistor comprising at least one third TMR film havinga third reference layer; and a fourth resistor comprising at least onefourth TMR film having a fourth reference layer. The third TMR film andthe fourth TMR film are substantially identical, and wherein the thirdreference layer and the fourth reference layer have an antiparallelmagnetic orientation. The first TMR film, the second TMR film, the thirdTMR film, and the fourth TMR film are substantially identical. The firstreference layer and the third reference layer have a parallel magneticorientation, and wherein the second reference layer and the fourthreference layer have a parallel magnetic orientation. The first TMR filmand the second TMR film each comprise: a seed layer; anantiferromagnetic layer disposed on the seed layer; a pinned layerdisposed on the antiferromagnetic layer; a spacer layer disposed on thepinned layer; a reference layer disposed on the spacer layer, whereinthe reference layer is either the first reference layer or the secondreference layer; a barrier layer disposed on the reference layer; and afree layer disposed on the barrier layer. The first TMR film has an R-Hcurve that has a positive slope and the second TMR film has an R-H curvethat has a negative slope. The first resistor and the second resistorhave the same resistance area (RA).

In another embodiment, a TMR sensor device comprises four resistors,wherein each resistor includes at least one tunnel magnetoresistive(TMR) film that includes a reference layer, wherein the TMR films areidentical in each resistor, and wherein the reference layer of at leasttwo TMR films have an antiparallel magnetic orientation. Each TMR filmcomprises: a seed layer; an antiferromagnetic layer disposed on the seedlayer; a pinned layer disposed on the antiferromagnetic layer; a spacerlayer disposed on the pinned layer; the reference layer disposed on thespacer layer; a barrier layer disposed on the reference layer; and afree layer disposed on the barrier layer. The seed layer and the spacerlayer comprise the same material. The seed layer and the spacer layereach comprise ruthenium. Each resistor has the same number of TMR films.Each resistor has the same resistance area (RA).

In another embodiment, a method of manufacturing a TMR sensor devicecomprises: forming a first tunnel magnetoresistive (TMR) film on asubstrate; forming a second TMR film on the substrate; annealing thefirst TMR film and the second TMR film in a magnetic field; andannealing the second TMR film a second time in a magnetic field. Duringthe annealing of the second TMR film a second time, the first TMR filmis not annealed. The magnetic field for the annealing the second TMRfilm a second time is less than the magnetic field for the annealing thefirst TMR film and the second TMR film. The annealing the second TMRfilm a second time is performed by laser annealing in a magnetic field.The laser annealing occurs with a laser beam size of less than 1 mm.During the annealing the second TMR film a second time in a magneticfield, the first TMR film is not masked.

In one embodiment, the TMR sensor is used in a camera operating as asingle axis sensor. An example of such a sensor is found in UnitedStates Patent Application Publication No.: 2019/0020822 A1, which isincorporated herein by reference. However, it is contemplated that theTMR sensor may be utilized as a two dimensional or even a threedimensional sensor. Additionally, it is contemplated that TMR sensor maybe integrated and utilized in inertial measurement unit technologiesother than cameras such as wearable devices, compasses, and MEMSdevices. Furthermore, the TMR sensor may operate as a position sensor, abridge angular sensor, a magnetic switch, a current sensor, orcombinations thereof. The TMR sensor may be used to focus a camera suchas a smart phone camera by using the TMR sensors as position and angularsensors. Also, TMR sensors have applicability in the automotive industryas switch, current, and angular sensors to replace current Hall,anisotropic magnetoresistance (AMR) and giant magnetoresistance (GMR)sensors. TMR sensors may also be used in the drones and roboticsindustry as position and angular sensors. Medical devices can alsoutilize TMR sensors for flow rate control for infusion systems andendoscope camera sensors among others. Thus, the TMR sensors discussedherein have applications well beyond smart phone cameras and thus shouldnot be limited to use as sensors for smart phone cameras. Furthermore,TMR sensors need not be arranged in a Wheatstone bridge arrangement, butrather, may be arranged in any number of manners.

By forming identical TMR films for all resistors, and then making thereference layers antiparallel for select TMR films, a Wheatstone bridgearray can be fabricated in both a time sensitive and cost effectivemanner.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A method of manufacturing a TMR sensor device,comprising: forming a first tunnel magnetoresistive (TMR) film on asubstrate; forming a second TMR film on the substrate; annealing thefirst TMR film and the second TMR film in a magnetic field; andannealing the second TMR film a second time in a magnetic field.
 2. Themethod of claim 1, wherein during the annealing of the second TMR film asecond time, the first TMR film is not annealed.
 3. The method of claim1, wherein the magnetic field for the annealing the second TMR film asecond time is less than the magnetic field for the annealing the firstTMR film and the second TMR film.
 4. The method of claim 1, wherein theannealing the second TMR film a second time is performed by laserannealing in a magnetic field.
 5. The method of claim 4, wherein thelaser annealing occurs with a laser beam size of less than 1 mm.
 6. Themethod of claim 1, wherein during the annealing the second TMR film asecond time in a magnetic field, the first TMR film is not masked. 7.The method of claim 1, wherein the TMR sensor device comprises: a firstresistor comprising at least one first TMR film having a first referencelayer, a first pinned layer, and a first spacer layer, the first spacerlayer sandwiched by and contacting both the first reference layer andthe first pinned layer; and a second resistor electrically coupled tothe first resistor comprising at least one second TMR film having asecond reference layer, a second pinned layer, and a second spacerlayer, the second spacer layer sandwiched by and contacting both thesecond reference layer and the second pinned layer, wherein the firstTMR film and the second TMR film are substantially identical, whereinthe first reference layer and the second reference layer have anantiparallel magnetic orientation, wherein the first pinned layer andthe second pinned layer have a parallel magnetic orientation, andwherein the magnetic orientation of the second pinned layer is parallelto the magnetic orientation of the second reference layer.
 8. The methodof claim 7, the TMR sensor device further comprising: a third resistorcomprising at least one third TMR film having a third reference layer;and a fourth resistor comprising at least one fourth TMR film having afourth reference layer.
 9. The method of claim 8, wherein the third TMRfilm and the fourth TMR film are substantially identical, and whereinthe third reference layer and the fourth reference layer have anantiparallel magnetic orientation.
 10. The method of claim 9, whereinthe first TMR film, the second TMR film, the third TMR film, and thefourth TMR film are substantially identical.
 11. The method of claim 10,wherein the first reference layer and the third reference layer have aparallel magnetic orientation, and wherein the second reference layerand the fourth reference layer have a parallel magnetic orientation. 12.The method of claim 7, wherein the first TMR film and the second TMRfilm each comprise: a seed layer; an antiferromagnetic layer disposed onthe seed layer; a pinned layer disposed on the antiferromagnetic layer,wherein the pinned layer is either the first pinned layer or the secondpinned layer; a spacer layer disposed on the pinned layer, wherein thespacer layer is either the first spacer layer or the second spacerlayer; a reference layer disposed on the spacer layer, wherein thereference layer is either the first reference layer or the secondreference layer; a barrier layer disposed on the reference layer; and afree layer disposed on the barrier layer.
 13. The method of claim 7,wherein the first TMR film has an R-H curve that has a positive slopeand the second TMR film has an R-H curve that has a negative slope. 14.The method of claim 7, wherein the first resistor and the secondresistor have the same resistance area (RA).
 15. The method of claim 1,wherein the TMR sensor device comprises: four resistors electricallycoupled to each other, wherein each resistor includes at least onetunnel magnetoresistive (TMR) film that includes a reference layer, apinned layer, and a spacer layer, the spacer layer sandwiched by andcontacting both the reference layer and the pinned layer, wherein theTMR films are identical in each resistor, wherein the reference layer ofat least two TMR films has an antiparallel magnetic orientation and thepinned layer of the at least two TMR films has a parallel magneticorientation, and wherein the at least two TMR films have their magneticorientation of their reference layers aligned parallel with respect totheir respective pinned layers.
 16. The method of claim 15, wherein eachTMR film comprises: a seed layer; an antiferromagnetic layer disposed onthe seed layer; the pinned layer disposed on the antiferromagneticlayer; the spacer layer disposed on the pinned layer; the referencelayer disposed on the spacer layer; a barrier layer disposed on thereference layer; and a free layer disposed on the barrier layer.
 17. Themethod of claim 16, wherein the seed layer and the spacer layer comprisethe same material.
 18. The method of claim 17, wherein the seed layerand the spacer layer each comprise ruthenium.
 19. The method of claim15, wherein each resistor has the same number of TMR films.
 20. Themethod of claim 15, wherein each resistor has the same resistance area(RA).